An integrated circuit (IC) is an electronic circuit formed using a semiconductor material, such as Silicon, as a substrate and by adding impurities to form solid-state semiconductor electronic devices (device, devices), such as transistors, diodes, capacitors, and resistors. Any reference to a “device” herein refers to a solid-state semiconductor electronic device unless expressly distinguished where used. Commonly known as a “chip” or a “package,” an integrated circuit is generally encased in hard plastic, forming a “package.” The components in modern day electronics generally appear to be rectangular black plastic packages with connector pins protruding from the plastic encasement. Often, many such packages are electrically coupled so that the chips therein form an electronic circuit to perform certain functions.
The software tools used for designing ICs produce, manipulate, or otherwise work with the circuit layout and circuit components on very small scales. Some of the components that such a tool may manipulate may only measure tens of nanometer across when formed in Silicon. The designs produced and manipulated using these software tools are complex, often including hundreds of thousands of such components interconnected to form an intended electronic circuitry.
A layout includes shapes that the designer selects and positions to achieve a design objective. The objective is to have the shape—the target shape—appear on the wafer as designed. However, the shapes may not appear exactly as designed when manufactured on the wafer through photolithography. For example, a rectangular shape with sharp corners may appear as a rectangular shape with rounded corners on the wafer.
Once a design layout, also referred to simply as a layout, has been finalized for an IC, the design is converted into a set of masks or reticles. A set of masks or reticles is one or more masks or reticles. During manufacture, a semiconductor wafer is exposed to light or radiation through a mask to form microscopic components of the IC. This process is known as photolithography.
A manufacturing mask or a photolithography mask is interchangeably referred to as a mask or a photo mask. A mask is usable for successfully manufacturing or printing the contents of the mask onto wafer. During the photolithographic printing process, radiation is focused through the mask and at certain desired intensity of the radiation. This radiation is usable to “dose” or add a material to a layer, “etch” or remove a material from a layer, or both. The focus and the dosing of the radiation has to be precisely controlled to achieve the desired shape and electrical characteristics on the wafer. A cut mask is a type of mask that is usable to cut or form a pattern in one or more layers of materials during a fabrication process.
A device generally uses several layers of different materials to implement the device properties and function. A layer of material can be conductive, semi-conductive, insulating, resistive, capacitive, or have any number of other properties. Different layers of materials have to be formed using different methods, given the nature of the material, the shape, size or placement of the material, other materials adjacent to the material, and many other considerations.
The illustrative embodiments recognize that the present methods and techniques for etching away material from a layer have an undesirable effect. For example, poor etch selectivity during etching, such as in using ion-beam etching on a photo-mask layer of a structure, some of the mask material will inevitably get removed in the process of etching. The redeposited material forms a fence-like formation around all or a part of the structure where etching was performed.
Often, the fence formation will remain standing above, or protruding beyond, a level of the structure, after the etching process has been completed, and follow-on remaining mask removal. Furthermore, the remaining photoresist mask is more likely to become hardened due to the heating effect in prolonged etching, especially when using high-energy etching conditions.
The illustrative embodiments recognize that a fence that is unintentionally created in this manner has undesirable effects on the performance of the structure. Therefore, a method for removing a residual photo-mask fence in the IBE etching process following the photolithography mask-creation step would be desirable.